Composite material bone implant

ABSTRACT

A composite bone implant. In some embodiments, one or more features are provided, such as markers for passageways, axial engagement of bone screws, sliding support of bone screws and/or a cannulated channel for a guide wire.

RELATED APPLICATIONS

This application is a National Phase of PCT Patent Application No.PCT/IB2010/050225 having International filing date of Jan. 18, 2010,which claims the benefit of priority of U.S. Provisional PatentApplication Nos. 61/213,991 filed on Aug. 6, 2009 and 61/205,160 filedon Jan. 16, 2009. The contents of the above applications are allincorporated herein by reference.

FIELD OF INVENTION

The present invention in some embodiments thereof, relates to compositematerial bone implant devices and to manufacturing methods for suchdevices.

As used herein, the terms “bone implant devices” and “bone implants” areintended to encompass hip joints, knee joints, shoulder joints, bonescrews, bone instruments, bone plates, and intramedullary nails,including proximal femur nails, typically including screw holes forreceiving bone fixation screws.

BACKGROUND OF THE INVENTION

Intramedullary nails (bone nails) have become a treatment of choice forthe fixation of bone fractures, especially fractures of long bones(e.g., the humerus, tibia and femur). Typically, bone nails arerod-shaped devices configured and constructed to be secured(interlocked) to a bone using one or more locking elements, such astransverse screws at one or both ends of the nail.

In many cases, the implant is constructed from metal, such as titanium,stainless steel or cobalt chromium. Although metallic implants providenumerous advantages, they also have a few drawbacks. Metal constructionnormally provides adequate bending strength, thus reducing problemsassociated with implant fracture and fatigue. However, the rigid metalimplant creates a relative high degree of stresses in certain regions ofthe bone, while, on the other hand, does not provide for sufficient loadtransfer resulting in stress shielding. Both high stress and stressshielding can cause bone deterioration and resorption, leading to areasof bone weakness and loss of bone support for the implant (e.g.,intramedullary nails and stem components of joint replacement systems).In addition, metals may result in artifacts in CT and MR imaging.Furthermore, metals such as stainless steel and cobalt chromium maycause biocompatibility problems related to corrosion and sensitizationreaction (mainly due to allergy to nickel).

Non-metal implants made of a lighter and more flexible material, yethaving sufficient strength for load bearing, have been suggested in thepast. In particular, composite material implants, for example formed ofpolymer reinforced with fibers, are discussed in U.S. Pat. Nos.4,750,905, 5,181,930, 5,397,358, 5,009,664, 5,064,439, 4,978,360,7,419,714 the disclosures of which are incorporated herein by reference.

U.S. Pat. No. 5,009,664 describes a tubular, curved marrow nail, made ofcarbon fibers, which are preferably knit in a crisscross fashion,saturated in a hardenable plastic, with a conically tapered distal tip.

U.S. Pat. No. 5,181,930 describes an implant comprising an elongatedcore formed of continuous filament fibers embedded in thermoplasticpolymer. The core is encased within a filler, made of a non-reinforcedpolymer which is molded around the core to proximate the final desiredshape of the implant. A sheath, composed of reinforced fibers embeddedin a polymer, is spiral wound around the filler, at angles(orientations) which may vary along the implant axis.

Although composite material implants can provide several advantages,they also have a few limitations. In contrast to metal, compositematerial implants are not visible under imaging devices (such asfluoroscopy), and hence their implantation as well as tracking duringfollow-up are difficult. U.S. Pat. No. 7,419,714 describes a bone screwor plate formed of a composite of polymer or ceramic material withreinforcing fibers, in which at least part of which are made of an X-rayabsorbent material. For bone nails or plates, accurate insertion of thescrews into the holes in the nail/plate is crucial to the success of theoperation, especially where no aiming device is used. The use ofinterlocking screws poses a problem in such implants, as the designatedholes at the nail ends (or at the plate), through which the screws areto be introduced, are not visible under fluoroscopy. The addition offibers made of material that absorbs X-rays may be insufficient; as suchfibers often do not adequately and accurately mark the hole. Also, inorder to improve the visualization of implant hole a large quantity ofsuch fibers might be required. In addition, with regards tointramedullary nails (or other implant construction that may comprise aweakened area), due to the composite material construction, theextremities of the nails at the area of the interlocking screw holes aremore prone to damage.

Further, although such composite materials may have several propertiesthat are claimed to be similar to those of bone, the composite materialconstruction may be less efficient under torsion loads.

Additionally, the instrumentation that is used with a metal implant,such as an insertion handle, is usually connected to the implant via athread at a proximal end of the implant. However, the composite materialconstruction (which is not isotropic as is metal), has less resistanceto shear forces, and damage (e.g., breakage) may result at the threadarea.

The present invention addresses improvements in the above-noted areas,and in other areas of composite bone implant technology.

SUMMARY OF THE INVENTION

There is provided in accordance with an exemplary embodiment of theinvention, a bone implant comprising:

a fiber reinforced polymer matrix body;

a passage through the body, open at opposite ends, and configured toreceive a bone fixation screw; and

a radiopaque marking for location and orientation of the passage.

Optionally, the passage is near a distal end of the body. Optionally oralternatively, the marking is comprised of at least one peripheral bandof radiopaque material located inside the passage. Optionally oralternatively, the radiopaque marking is comprised of a plurality oflocalized areas of radiopaque material around the outside of thepassage. Optionally, the radiopaque material is in the form of two rodslocated at each end of the passage.

In an exemplary embodiment of the invention, the radiopaque markingcomprises a metal element extending along a longitudinal axis of thebody.

In an exemplary embodiment of the invention, the implant is a boneplate, and the marking comprises at least one thin metal wire extendingin a plane which is not subject to substantial bending strain.

In an exemplary embodiment of the invention, the implant is cannulatedand the radiopaque marking is a thin metal layer extending along aninner surface of a lumen running through the implant body.

In an exemplary embodiment of the invention, the radiopaque marking ispresent in a quantity and configuration which results in levels ofartifacts upon CT or MRI which do not significantly interfere withvisualization.

In an exemplary embodiment of the invention, the localized areas arediametrically opposed, and are equally spaced from a longitudinal axisthe respective passages, whereby correct orientation for insertion ofthe fixation screw into the passage is indicated when the rods at eachend of a passage appear as single dots under fluoroscopic imaging.

In an exemplary embodiment of the invention a composite implant,optionally such as described above, is provided with a guide channel fora guide wire. Optionally such a channel is formed of a metal tube.

There is provided in accordance with an exemplary embodiment of theinvention, a bone implant comprising:

a fiber reinforced polymer matrix composite body;

a connector at a proximal end of the body configured to be attached toan implant insertion tool in a single orientation, and adapted forbearing torsion applied by the insertion tool.

In an exemplary embodiment of the invention, a kit is provided includinga bone implant as described above and an insertion tool including aconnector interface having an alignment element adapted to engage with acomplementary element of the connector in the single orientation.Optionally, the connector includes an internally threaded recess.Optionally or alternatively, a proximal end face of the connectorincludes a plurality of radial slots at extending inwardly from aperiphery at the proximal end. Optionally or alternatively, theconnector has a hexagonal configuration.

In an exemplary embodiment of the invention, the connector includes abayonet configuration.

In an exemplary embodiment of the invention, the connector includes ametal insert configured to receive an implant tool.

There is provided in accordance with an exemplary embodiment of theinvention, an end cap for a bone implant wherein the implant comprises afiber reinforced polymer body and a connector at a proximal end of thebody for receiving an insertion tool; wherein the end cap is configuredto cover the connector when the implant is in place to inhibit tissuegrowth from preventing access to the connector for subsequent implantremoval. Optionally, the connector is an internal recess and the end capis externally configured to fit in the recess. Optionally oralternatively, the end cap includes a radiopaque marking. Optionally oralternatively, the end cap is formed of the same material as the implantbody.

There is provided in accordance with an exemplary embodiment of theinvention, a bone implant comprising:

a body formed of a reinforced polymer matrix, and

a passage through the body configured to receive a bone fixation screw,wherein the passage is configured to resist axial withdrawal of a bonefixation screw received therein. Optionally, the passage is a circularhole having a diameter that is smaller than an outside diameter of thescrew. Optionally or alternatively, the implant comprises an elongatedlongitudinal slot at a proximal end of the body configured to slidablyreceive a bone screw therein, and to resist axial withdrawal of areceived bone screw.

Optionally or alternatively, the resistance to axial withdrawal isprovided by a ridge in an internal surface the circular hole and/or theslot. Optionally or alternatively, the passages are unthreaded.

There is provided in accordance with an exemplary embodiment of theinvention, a bone implant comprising:

a body formed of a reinforced polymer matrix; and

a metal element incorporated in the body. Optionally, the metal elementis an insert at a proximal end of the body configured to receive animplant insertion tool. Optionally or alternatively, the metal elementis a smooth metal coating on the implant body.

In an exemplary embodiment of the invention, the insert is a couplingelement. Optionally or alternatively, the insert is a structuralelement.

There is provided in accordance with an exemplary embodiment of theinvention, a bone implant comprising:

a body having a core constructed and configured to resist mainly bendingforces; and

a portion enclosing the core constructed and configured to resist mainlytorsional forces;

wherein the core and the surrounding portion are comprised ofsubstantially linearly extending comingled long carbon and polymerfilaments in a polymer matrix, and

wherein at least part of the exterior surface is covered with a layer ofmetal. Optionally or alternatively, the enclosing portion is braided.

In an exemplary embodiment of the invention, the implant is in the formof an intramedullary nail, and enclosing portion is comprised of twolayers of filaments helically wound in opposite directions. Optionally,the implant includes an outer layer comprised of linearly extendingfilaments.

In an exemplary embodiment of the invention, a proximal end is comprisedof:

a core of linearly extending filaments;

at least two layers of filaments helically wound in opposite directions;and an outer layer comprised of filaments in a circular spiralconfiguration. Optionally, the helically wound filaments lie at about±45 degrees to a longitudinal axis of the nail. In an exemplaryembodiment of the invention, the core includes a substantially central,axially extending lumen.

In an exemplary embodiment of the invention, the implant is in the formof a bone plate. Optionally, the plate further includes a body moldedaround a plurality of passages configured to receive bone fixationscrews. Optionally, the plate includes a radiopaque marking incorporatedinto the body.

There is provided in accordance with an exemplary embodiment of theinvention, a bone fixation screw comprising:

a composite core formed of a threaded, reinforced polymer body; and

a metal exterior surface on the core. Optionally, the metal exteriorsurface is a plating having a smooth surface which does not promoteintegration with surrounding bone tissue when the screw has beenimplanted. Optionally or alternatively, the metal surface is comprisedof titanium or a titanium alloy. Optionally or alternatively, the metalsurface is thin enough that it does not cause artifacts in CT or MRIimages that would interfere significantly with visualization. Optionallyor alternatively, the metal surface is threaded.

In an exemplary embodiment of the invention, the screw threads areoversized or mismatched in pitch relative to screw holes in a boneimplant configured to receive the screws. Optionally or alternatively, aportion of the composite core penetrates an inner surface of the metalthreads.

In an exemplary embodiment of the invention, an interface between thecomposite core and the metal surface includes complementary projectionsand recesses.

In an exemplary embodiment of the invention, the material comprising themetal surface is crimped around proximal and/or distal ends of thecomposite core of the screw.

There is provided in accordance with an exemplary embodiment of theinvention, a proximal femur (PF) nail assembly comprising:

an elongated stem having a proximal end; and

a passage through the proximal end of the nail oriented at an angle to alongitudinal axis of the nail, the passage being oriented for anchoringthe nail in the neck and head of the femur; and

a bone fixation screw received in the passage,

wherein the nail is a composite comprised of a reinforced polymermatrix. Optionally, the assembly includes a further passage isconfigured to receive an anti-rotation pin, wherein the anti-rotationpin passage extends parallel to the proximal end fixation screw passage.Optionally or alternatively, the screw is comprised of the samecomposite material as the nail, and includes a threaded metal shell.

In an exemplary embodiment of the invention, the assembly includes: aninsertion tool connector at the proximal end comprising an axiallyextending bore; and

a cover configured to be received in the bore after the implant is inplace to prevent bone or other tissue regrowth in the bore.

In an exemplary embodiment of the invention, the assembly includes apassage at a distal end of the body configured to receive a bonefixation screw; and

a radiopaque marking for the location of the distal passage.

In an exemplary embodiment of the invention, the anti-rotation pin ismetal.

In an exemplary embodiment of the invention, the passage for theproximal end fixation screw includes a holder for the screw.

There is provided in accordance with an exemplary embodiment of theinvention, a tool for removing a bone implant, wherein the implantincludes a body having an axial opening at a proximal end thatcommunicates with a transverse passage, the tool comprising:

first and second arms;

a first transverse tip at a distal end of the first arm;

a second transverse tip at a distal end of the second arm extending inan opposite direction from that of the first tip; and

a handle mechanism operable to move the first and second tips between aretracted position in which the tips are close to each other and anextended position in which the tips are separated, wherein the tips aresized and configured such that, in the retracted position, the tool isinsertable into the axial opening in the implant, and in the extendedposition, the tips are within opposite sides of the screw passage,whereby axial force can be applied to withdraw the implant from insidean opening in a bone. Optionally, the first and second arms are crossed,and are connected at a pivot located between distal and proximal ends ofthe arms.

There is provided in accordance with an exemplary embodiment of theinvention, a bone implant drilling assembly comprising:

a power unit; and

a flexible cable connected between the power unit and a drill bit totransfer torque from the power unit to the drill bit. Optionally, theflexible cable is contained in an angled housing; and including:

couplings at opposite ends of the cable for attachment to the power unitand the drill bit. Optionally or alternatively, the power unit containedwithin the housing. Optionally or alternatively, the assembly isconstructed for disposal after a single use.

There is provided in accordance with an exemplary embodiment of theinvention, a method of forming a bone plate comprised of a fiberreinforced thermoplastic polymer composite comprising:

pre-forming a bone plate based on average anatomical data;

obtaining specific anatomical data concerning an actual implant site fora particular patient;

heating the pre-formed bone plate and applying force to bend thepre-formed bone plate to the required shape; and

cooling the bent bone plate in a manner which allows it to retain itsbent shape without substantial change in its other properties.Optionally, the specific anatomical data is obtained by directmeasurement of a patient's implant site during a surgical procedure.Optionally, the specific anatomical data is obtained radiologically orby an MRI or CT of a patient's implant site.

There is provided in accordance with an exemplary embodiment of theinvention, a method of forming a bone nail comprised of a fiberreinforced thermoplastic polymer composite body and including a bend toconform to a particular implant site comprising:

pre-forming the bone nail without a bend;

heating the pre-formed bone nail while applying force to bend thepre-formed bone plate to the required shape; and

cooling the bent bone nail in a manner which allows it to retain itsbent shape without substantial change in its other properties.

Unless otherwise defined, all technical and/or scientific terms usedherein have the same meaning as commonly understood by one of ordinaryskill in the art to which the invention pertains. Although methods andmaterials similar or equivalent to those described herein can be used inthe practice or testing of embodiments of the invention, exemplarymethods and/or materials are described below. In case of conflict, thepatent specification, including definitions, will control. In addition,the materials, methods, and examples are illustrative only and are notintended to be necessarily limiting.

BRIEF DESCRIPTION OF THE FIGURES

Some embodiments of the invention are herein described, by way ofexample only, with reference to the accompanying drawings. With specificreference now to the drawings in detail, it is stressed that theparticulars shown are by way of example and for purposes of illustrativediscussion of embodiments of the invention. In this regard, thedescription taken with the drawings makes apparent to those skilled inthe art how embodiments of the invention may be practiced.

In the drawings:

FIG. 1 is a side elevation of bone implant in accordance with someembodiments of the present invention;

FIG. 2A is a cross-sectional view taken along line 2-2 in FIG. 1;

FIG. 2B is a pictorial illustration of an end cap for the proximal endof an implant according to some embodiments of the invention;

FIG. 3A is an enlarged fragmentary perspective view of the distal end ofFIG. 2A showing a radiopaque marking for a screw hole according to someembodiments of the invention;

FIG. 3B is an enlarged fragmentary perspective view similar to FIG. 3Ashowing an alternative radiopaque marking for a screw hole according tosome embodiments of the invention;

FIG. 3C is an enlarged perspective view of the proximal end of theimplant of FIGS. 1 and 2A certain details of the internal constructionof a screw hole and an elongated slot according to some embodiments ofthe invention;

FIG. 4 is perspective view seen from the proximal end of a bone nailshowing details of a connector for an insertion tool according to someembodiments of the invention;

FIG. 5 is a perspective view similar to FIG. 4 showing a variation ofthe proximal end of a bone nail according to some embodiments of theinvention;

FIGS. 6A-6C are respectively schematic illustrations of a bone nail, ablowup a proximal end of the bone nail, and a blowup a distal end of thebone nail, according to some embodiments of the present invention;

FIG. 7 is a side elevation of a cannulated bone implant in accordancewith some embodiments of the present invention;

FIG. 8 is a view rotated 90 degrees from FIG. 7;

FIG. 9A is a cross-sectional view taken along line 9-9 in FIG. 8;

FIG. 9B is an enlarged fragmentary view of the distal end of an implantas shown in FIGS. 8 and 9;

FIG. 10A is an intramedullary nail including a metal nut to impart addedstrength to the connection between the implant, according to someembodiments of the present invention;

FIGS. 10B and 10C are illustrations of T shaped nuts according to someembodiments of the invention;

FIG. 11 is a schematic illustration of a bone plate;

FIGS. 12A-12D are side elevations of bone fixation screws according tosome exemplary embodiments of the invention;

FIG. 13A illustrates a proximal femur (PF) nail, according to someembodiments of the invention;

FIGS. 13B and 13C illustrate bone screws which may be used as leg screwswith the PF nail of FIG. 13B, according to some embodiments of theinvention;

FIG. 14A-14B show an implant removal tool according to some embodimentsof the invention;

FIGS. 15A and 15B are schematic illustrations a bone drill andradiolucent connector that allows for unobstructed fluoroscopicvisualization, according to some embodiments of the invention;

FIGS. 16A-16G illustrate a bayonet coupling for the connection betweenthe implant and an insertion tool, according to some embodiments of theinvention; and

FIGS. 17A and 17B illustrate a tool for bending a bone nail to a desiredconfiguration, according to some embodiments of the invention;

FIG. 18 shows an example of a drill guide and insertion tool for usewith an implant, according to some of the implant embodiments.

DETAILED DESCRIPTION OF SEVERAL EMBODIMENTS OF THE INVENTION

The present invention, in some embodiments thereof, relates to compositematerial bone implant devices and to manufacturing methods for suchdevices. More particularly, but not exclusively, the invention relatesto such devices and methods as applied to implant devices formed offiber-reinforced polymer matrices or self-reinforcing polymers.

According to an aspect of some embodiments of the invention, implantsare formed of a matrix of polymer material such as polyarylether ketone(PAEK), polyether ether ketone (PEEK), or other polyketone basedpolymers. Implants according to some embodiments of the invention mayalso be formed of a matrix polymer material such as but not limited topolyphenylene, polyphenylsulfone, or polysulfone. In all suchembodiments, reinforcing fibers may included in the matrix. Optionally,these may be formed of carbon, ultrahigh density polyethylene (UHDPE),aramid polymers, or ceramic fibers such as glass. Optionally, two ormore of these may be used together.

According to an aspect of some embodiments of the invention, the implantcan be manufactured of a composite matrix material such as polyphenyleneor UHDPE.

According to an aspect of some embodiments of the invention, in a boneimplant having passages for receiving bone fixation screws, radiopaquemarking visible under fluoroscopy is provided to show the locations ofthe passages. Optionally, the marking is in the form of at least oneperipheral band of radiopaque material located inside each passage. Insome exemplary embodiments, there are two spaced bands. In otherexemplary embodiments, there is a single long band. Optionally, the longband extends substantially the length of the passage.

According to an aspect of some embodiments of the invention, the markingis in the form of a plurality of localized areas of radiopaque materialaround the outside of each passage. In some exemplary embodiments, tworods or pins are located at each end of each passage running parallel tothe passage. Optionally, the rods are short compared to the length ofthe passage. Optionally, the rods are diametrically located, and areequally spaced from a longitudinal axis of the respective passages,whereby correct orientation for insertion of the fixation screw into thepassage is indicated when the rods at each end of a passage appear assingle dots when, for example, the X-ray beam is parallel to thepassage.

.According to an aspect of some embodiments of the invention, theimplant is a bone nail, and a radiopaque marking is formed by at leastone metal wire extending along a longitudinal axis of the body, inaddition to or instead of the marking described above. The wire isinterrupted by the fixation screw passages, so that the locations of thepassages are indicated by the interruptions.

According to an aspect of some embodiments of the invention, the implantis a bone plate, and the radiopaque marking is formed by at least onemetal wire extending in a plane which is subject to minimal changes inlength during use due to substantial bending. The wire may beinterrupted by the fixation screw passages, so that the locations of thepassages are indicated by the interruptions.

According to an aspect of some embodiments of the invention, the implantis a cannulated bone nail and the radiopaque marking is a thin metallayer extending along an inner surface of a lumen running through theimplant body. The metal layer is interrupted where the fixation screwpassages cut through the lumen, so that the locations of the passagesare indicated by the interruptions.

According to an aspect of some embodiments of the invention, theradiopaque marking is radiopaque filler, optionally barium, bariumsulfate, zircona, etc. which can be pre-filled into the polymer matrixmaterial in various concentration from 1-2 up to 40% by volume or mass,and incorporated in the implant. The filler is interrupted by thefixation screw passages, so that the longitudinal locations of thepassages are indicated by the interruptions.

According to an aspect of some embodiments of the invention, to addhardness and strength to the implant, a metal or ceramic element is alsoembedded in the polymer implant. In some exemplary embodiments of theinvention, the element is a nut embedded into the implant duringmanufacturing of the implant.

Alternatively, or additionally, in some exemplary embodiments of theinvention, a metal layer may be applied to the surface of the implant,for example, as plating. The coating is made as smooth as possible todiscourage integration with the surrounding bone tissue.

Optionally, the embedded elements and the coating are formed oftitanium, titanium alloy or tantalum. Optionally, other suitable metalsor metal alloys may be used.

According to an aspect of some embodiments of the invention, fixationscrews, for example, for an intramedullary nail or bone plate are formedof the same composite material as the nail or bone plate itself.Optionally or additionally, the threads of the fixation screws areplated with a thin coating of metal such as titanium, titanium alloy(for example, Ti6A14V), tantalum, gold, or any other biocompatible metalor metal alloy to improve shear strength, and surface hardness. Themetal plating is thick enough to provide the needed additional strength,but thin enough that it does not cause an unacceptable level of CT orMRI image artifacts. In case artifacts are caused, they are sharplydecreased compared to similar implants made of metals. The metal coatingis made as smooth as possible to prevent attachment of re-grown tissueor bone to the threads, or the screw body, which would hinder removal ofthe screw if the implant must later be removed.

Normally, the bone fixation screws are threaded into the bone to anchoran implant such as a bone nail or plate. However, it is sometimesdesirable or necessary, for example, in the case of osteoporotic boneswhich are soft, to lock the screw also into the implant to prevent axialwithdrawal. According to an aspect of some embodiments of the invention,at lest some of the screw holes are slightly smaller than the outsidediameter of the screw, or conversely, the outside diameter of the screwsis slightly larger than the screw holes. Optionally, the screw holes maybe threaded or unthreaded.

When the screw holes are unthreaded, during insertion, the screw pushesthe implant material aside, or cuts its own thread, and locks into thesurrounding material. In embodiments having threaded screw holes, thethreads of the holes and the screws lock together due to the dimensionaldisparity.

Alternatively, the thread pitch for the screws and holes may bedifferent. In such a case, the screw locks into the hole due to thepitch disparity.

According to an aspect of some embodiments of the invention, when thereis a need for the screw to lock into the implant, at least some of thescrew holes include a circumferential ring or ridge that reduces thediameter of the hole in a localized area.

When the screw is inserted, it deforms the material of the ridge or cutsa thread allowing it to lock into the implant.

It should also be noted that according to some embodiments of theinvention, bone screws as described herein may be used as standaloneimplements to attach two parts of broken bone, without a nail or plate.

According to an aspect of some embodiments of the invention, a bone nailis formed with a longitudinal slot at its proximal end. After the nailhas been attached to the broken bone at its distal end by a bone screw,and the broken parts of the bone have been aligned, the surgeon canapply compression to the fracture site by attaching a screw to the bonethrough the slot and pulling the nail against the screw in the slot,optionally using the implant insertion tool. One or more other screws atthe proximal end may be added to anchor the nail.

According to an aspect of some embodiments of the invention, the slotmay include a ridge or rib to prevent withdrawal of the screw from theslot, as in the case of the round screw hole described above.

According to an aspect of some embodiments of the invention, a bone nailimplant includes a connector, optionally an internally threaded recessat its proximal end, for attachment of an insertion tool havingcomplementary external threads.

Optionally, the recess is configured with a plurality of radial slots onits end surface. Alternatively, the end may have a hexagonal externalconfiguration capable of bearing torsion.

Optionally, the connection configuration permits only a single manner ofconnection, thus assuring connection in the proper orientation

According to an aspect of some embodiments of the invention, a closurecap is provided for the open end of the connector, optionally formed ofthe same material as the implant body, optionally without the fibers,and includes external threads which engage the internal threads of theconnector. Closing the connector serves to inhibit tissue growth in theopen connector end that could hinder access to the connector by aremoval tool for subsequent implant removal if necessary.

Optionally, a closure cap as described includes radiopaque marking.

Optionally, according to some exemplary embodiments of the invention,the nail may be cannulated. For such a construction, the core includes asubstantially central, axially extending lumen. Optionally, according tosome embodiments of the invention, the inner surface of the lumen has ametal coating which serves as a marking.

According to an aspect of some embodiments of the present invention, anintramedullary nail is formed with a core constructed and configured toresist mainly bending forces (for example, about 75% or more of theforces encountered are bending forces), and a sleeve enclosing the core,for resisting mainly torsional forces (for example, about 75% or more ofthe forces encountered are torsional forces). In some exemplaryembodiments, the core and an outer layer are formed of substantiallylinearly extending comingled long carbon and polymer filaments in apolymer matrix. The sleeve is intermediate the core and the outer layer.According to some embodiments, the sleeve is braided, i.e., it is formedof two oppositely wound helical layers, for example, at ±45 degrees.Optionally, the exterior is coated with a layer of metal such astitanium, titanium alloy or tantalum.

According to some embodiments of the invention, at the proximal end, thefibers in one or more layers are oriented helically with very smallpitch, or optionally, circularly, around the main axis of the nail. Thatorientation increases the strength of the engagement of the nail and theinsertion tool.

Optionally, if the implant is likely to experience high local stressesat the installation site, or during insertion or removal, an insert maybe provided, optionally in the form of metal nut

Alternatively, or additionally, the surface of the implant may beprovided with a metal coating. The net, the metal insert, and thecoating are optionally formed of titanium or titanium alloy, or anyother suitable and desired metal or metal alloy.

According to an aspect of some embodiments of the present invention, abone plate has a woven or braided body formed of substantially linearlyextending comingled long carbon and polymer filaments in a polymermatrix.

Optionally, passages for receiving bone fixation screws are formed inthe molding process when the plate is fabricated. Optionally, thepassages are formed, for example, by machining, after the plate has beenfabricated.

According to an aspect of some embodiments of the present invention, abone plate is preformed of a reinforced thermoplastic polymer, based onaverage anatomical data, and then bent to a final shape beforeimplantation based on specific anatomical data concerning the actualimplant site for a particular patient. According to some exemplaryembodiments, the final shaping is done by heating the pre-formed implantand applying force to bend it to the required shape, then cooling thebent implant in a manner which allows the implant to retain its bentshape without substantial change in its other properties.

Optionally, the specific anatomical data is obtained by directmeasurement of the patient's implant site during a surgical procedure,or even visually. Optionally, the specific anatomical data is obtainedradiologically or by an MRI or CT of the patient's implant site.

According to an aspect of some embodiments of the invention, a bonefixation screw may be formed of the same fiber reinforced or selfreinforcing polymer materials as the implant itself. Optionally, toprovide added shear strength, the screw threads are coated with a thinlayer metal, for example, titanium, titanium alloy, tantalum, gold, orany other biocompatible metal or metal alloy. The metal coating shouldbe thick enough to provide the needed additional strength, but thinenough that it does not cause artifacts in CT images or MRIs.

According to an aspect of some embodiments of the present invention, aproximal femur (PF) nail includes an elongated stem having a proximalend and at least one passages through the proximal end oriented at anangle to a longitudinal axis of the nail to receive a proximal end bonefixation screw for anchoring the nail in the neck and head of the femur,wherein the nail is comprised of a reinforced polymer matrix.Optionally, the PF nail includes a further passage configured to receivean anti-rotation pin, which passage extends parallel to the proximal endfixation screw passage. Optionally according to some exemplaryembodiments of the invention, a PF nail includes radiopaque markings forat least one passage.

Optionally according to some exemplary embodiments of the invention, aPF nail includes an insertion tool connector comprising an axiallyextending bore at a proximal end of the nail; and a cover configured tobe received in the bore after the nail has been implanted to preventtissue and bone regrowth in the bore.

Optionally, in a PF nail as described above, the reinforced polymermatrix includes at least one layer of reinforcing fibers extendinglongitudinally in the nail body.

Optionally, in a PF nail as described above, the passage for theproximal end fixation screw (also called a leg screw) is configured toreceive a holder for the screw.

Optionally, the PF nail is long enough to treat femoral shaft fracturesin addition to the proximal femur fractures.

According to an aspect of some embodiments of the invention, a boneimplant includes a PF nail as described above, and a leg screw foranchoring the implant in the neck and head of the femur. Optionally, theleg screw is formed of the same material as the nail. Optionally, thescrew is formed of metal, for example, a titanium alloy. Optionally, theimplant includes an anti-rotation pin extending parallel to the legscrew.

According to an aspect of some embodiments of the invention, a bonescrew for a PF nail as described above is formed of a core of the samematerial as the nail. Optionally, the screw includes a metal shellsurrounding the reinforced polymer core. Optionally, the metal shell isthreaded at a distal end. Optionally, a portion of the polymer corepenetrates an inner surface of the metal threads. Optionally, aninterface between the polymer core and the shell includes complementaryprojections and recesses. Optionally, the metal shell is crimped aroundproximal and/or distal ends of polymer core of the screw.

According to an aspect of some embodiments of the present invention, animplant removal tool is constructed to engage an installed implantthrough an axial opening at a proximal end of the implant thatcommunicates with a transverse passage configured to receive a bonefixation screw.

According to some exemplary embodiments, the tool includes first andsecond arms, each having a transverse tip at its distal end, and a levermechanism operable to move the first and second tips between a retractedposition in which the tips are close to each other and an extendedposition in which the tips are separated,

According to some exemplary embodiments, the tips are sized andconfigured such that, in the retracted position, the tool is insertableinto the axial opening in the implant, and in the extended position, thetips are within opposite sides of one of the screw passages, optionallythe slot used to compress the fracture site, whereby axial force can beapplied to withdraw the implant from inside an opening in a bone.

According to some exemplary embodiments, the first and second arms arecrossed as in a pair of scissors, and are connected at a pivot locatedbetween distal and proximal ends of the arms.

According to some exemplary embodiments, the first and second arms areopposed but not crossed, and are connected at a pivot point located atproximal ends of the arms. Optionally, the pivot includes a spring whichmaintains the tips in the extended position when the spring is in anuncompressed state, and draws the tips to their retracted position whenit is compressed.

According to an aspect of some embodiments of the present invention, abone drill for drilling a bone to receive a bone implant includes apower unit and a substantially radiolucent angled connector configuredto be fitted between the power unit and a drill bit, According to someexemplary embodiments, the connector includes an angled housing,couplings for attachment to a drill power unit and a drill bit, and aflexible cable. Optionally, the connector is constructed for disposalafter a single use.

According to an aspect of some embodiments of the invention, theconnection between the implant and an insertion tool is a bayonetcoupling rather than threaded.

According to an aspect of some embodiments of the invention, a bone nailwhich will have a bend as part of its final shape is preformed without abend, and then subjected to heat and a bending force in a mold. The bentnail is then cooled according to a protocol which allows it to retainits bent shape and other original properties.

DETAILED DESCRIPTION OF SOME EMBODIMENTS OF THE INVENTION

Before proceeding with the detailed description of the embodiments ofthe invention, it is noted that the devices and parts to be describedare all formed of a matrix of Thermoplastic polymer material orthermoset polymeric resins. thermoplastic polymers such as polyaryletherketone (PAEK), polyether ether ketone (PEEK), other polyketone basedpolymers such as OXPEKK®, made by Oxford Performance Materials, Enfield,Connecticut, polyphenylene, polyphenylsulfone, polyamide-imide,polyphenylene sufide or polysulfone, or similar. thermoset polymericresins such as epoxy, polyester, polyimide or bismaleimide Reinforcementmay be provided by carbon and/or ultrahigh density polyethylene (UHDPE)fibers such as Spectra® from Honeywell, of Colonial Heights, Virginia,or Dyneema®, from DSM Dyneema of Heerlin, the Netherlands, aramidfibers, e.g., Kevlar®, from DuPont of Wilmington, Delaware, quartz,basalt, polyethylene, boron or glass. Optionally, two or more of thesemay be used together. Optionally, the fibers constitute 40 to 80 percentby volume of the implant material. In an exemplary embodiment, thefibers constitute 60 percent by volume of the implant material.

Alternatively, according to some embodiments of the invention, theimplant can be manufactured of a self reinforcing composite materialsuch as Dyneema.

Turning now to the drawings, FIGS. 1 and 2A respectively illustrate aside elevation and a cross-sectional view taken along line 2-2 in FIG. 1of an intramedullary nail in accordance with some embodiments of theinvention. The nail, generally denoted at 30 is comprised of anelongated body 32 formed of a fiber reinforced polymer matrix asdescribed above.

At a proximal end 34, body 30 includes one or more generally round screwholes (one being shown by way of example at 38), extending through body32, a longitudinally elongated slot 40, also extending through body 32,and an crown portion generally denoted at 42, As shown in FIGS. 4 and 5,proximal end 34 includes a threaded axial bore 44 extending into anconnector portion 42, configured to engage an insertion tool asdescribed below. Optionally, bore 44 extends axially a sufficientdistance to communicate with the proximal end of slot 40 to facilitateaxial compression of the nail to the bone prior to insertion of all theinterlocking screws, and for connection of an implant removal tool, alsoas described below.

At a distal end 36, body 32 includes one or more generally round screwholes (one of which is indicated at 46) extending sidewardly throughbody 32, and optionally, one or more generally round screw holes 48extending for example at a 90 degree angle to screw hole 46.

Optionally, some (or all) of the screw holes may be threaded, asindicated by hole 38, or unthreaded, as indicated by holes 46 and 48.

Implants as described above formed of fiber reinforced polymer, may befabricated in any of several conventional ways, generally using heat andpressure such as compression molding, or injection molding. These arewell known to persons of ordinary skill in the art, so furtherdescription is omitted in the interest of brevity. In the case of selfreinforcing polymers such as Dyneema, the implant may be fabricated bythe known technique of holding a bundle of thermoplastic fibers orientedin a desired direction, and rapidly heating and cooling the fiber bundleunder pressure in a mold so the outer the fibers melt together to createthe matrix, while the core fibers do not have time to melt, and thuskeep their very high strength,

According to some embodiments of the invention, radiopaque markings areprovided to assist the surgeon in locating screw holes 46 and 48, etc.and slot 40 for accurate insertion of bone fixation screws, not shown,but as described below. The markings may take various forms, asillustrated in FIGS. 1 and 2, FIGS. 3A through 3C, and also FIGS. 9A and9B.

By way of example, screw hole 46 is marked by four short metal rods orpins 50, two at each end of hole 46, best illustrated in FIGS. 2A and3A. Rods 50 extend parallel to screw hole 46 and are equally spaceddiametrically from the center of the hole, As best seen in FIG. 3A, rods50 a and 50 c are located at one end of screw hole 46, and rods 50 b and50 d are located at the opposite end. Rods 50 a and 50 b are aligned onone side of screw hole 46, and rods 50 c and 50 d are aligned on theopposite side.

During the implant procedure, the implant site is visualizedfluoroscopically. As will be understood, when hole 46 and markings 50are viewed from the proper axial position for insertion of the fixationscrews, rods 50 a and 50 b and 50 c and 50 d respectively appear assingle dots equally spaced diametrically from the center of the hole(see FIG. 1). By inserting the screw at the center thus indicated, andwith the rods appearing as single dots, proper positioning of the screwis achieved.

Another form of radiopaque marking is illustrated in FIG. 3A. Here, themarkings comprise two thin metal rings 52 a and 52 b located inside ascrew hole 54. Rings 52 may be formed by plating the surface of hole 54,or may be inserted into the hold and radially expanded or may beinserted into the body of the implant as part of the molding process, Aswill be appreciated by those skilled in the art, when screw hole 54 isvisualized fluoroscopically from the proper axial orientation, the rings52 a and 52 b appear as a single circular ring.

FIG. 3B illustrates a variation of the marking arrangement of FIG. 3A,in which a single metal tube 58 is provided extending substantially theentire length of the inside of a screw hole 56. As will be appreciated,when such a marking is viewed at the proper axial orientation forinsertion of the fixation screw, it appears as an undistorted circle.

It should be noted that marking is needed mainly for screw holes at thedistal part of the nail. For the proximal end, an external aiming devicemay be used that is attached to the proximal end of the nail duringinsertion, according to conventional practice

Other forms of radiopaque markings for the screw holes, 46 and 48 arealso possible. For example, body 32 may include one or morelongitudinally extending wires, such as axial wire 59 (see FIG. 2). Inthe case of a bone plate, in some exemplary embodiments, the wire isoptionally located in a plane which subject to minimum change of lengthdue to bending.

In the case of a cannulated nail for use in long bones such as the femurand tibia, a marking may optionally take the form of a thin metal tubeon the inside of an internal lumen (see description below). Anotheroption is to include a quantity of radiopaque filler, for example,barium, in the polymer matrix.

It should be understood such alternatives, the screw holes causediscontinuities which indicate only longitudinal location, but notprovide drilling direction information.

Suitable metals for use as markings include, tantalum, gold, or otherbiocompatible materials having high atomic numbers. In an exemplaryembodiment, the metal is tantalum.

In all instances, it is to be understood that the size of the markingsshould be sufficient to be clearly visualized fluoroscopically, but notlarge enough to cause significant artifacts in CT images or MRI. In someexemplary embodiments, wires such as 59 may have a diameter in the rangeof 0.05-0.4 mm, for example, 0.2 mm. Rods 50 may have a diameter in therange of 0.2-1 mm, for example, 0.7 mm.

As previously mentioned, the proximal end of nail 30 comprises aconnector including a threaded bore 44 for attachment of an implantinsertion tool. Referring now to FIG. 2B, there is shown an end cap 60configured to be threadedly received within threaded bore 44 uponcompletion of the nail implant procedure.

The purpose of end cap 60 is to provide a closure for bore 44 whichprevents regrowth of bone or other tissue inside the bore which wouldhinder insertion of an implant removal tool should removal of theimplant later be necessary. End cap 60 includes slots 62 at its end tofacilitate its own insertion and removal, but other configurations arepossible, as will be recognized by persons skilled in the art.

End cap 60 may optionally be formed of the same matrix material (forexample PEEK) as body 32, without fibers, and may be fabricated in anyconventional or desired manner. End cap material can include radiopaquemarking, for example, spaced rods or pins 64.

Normally, an implant such as a bone nail or plate is attached to theunderlying bone by the fixation screws (not shown) which are threadedinto the bone through holes in the bone implant. However, in someinstances, such as for osteoporotic bones that are soft, it may bedesirable or even necessary to lock the screw also into the implant toprevent axial withdrawal. In some embodiments of the invention, this isaccomplished by making at least some of the screw holes slightly smallerthan the outside diameter of the screw, or conversely, by making theoutside diameters of the screws slightly larger than the screw holes.Optionally, the screw holes may be threaded or unthreaded. When thescrew holes are unthreaded, during insertion, the screw pushes theimplant material aside, or cuts its own thread, and locks into thesurrounding material. In embodiments having threaded screw holes, thethread pitch may be different on the holes and the screws so the twolock together due to the dimensional or pitch disparity.

Alternatively, to provide for locking the screw into the implant, atleast some of the screw holes such as 38 at the proximal end of implant30 may include a ridge or rib similar to rib 154 shown in FIG. 3C thatreduces the diameter of the hole in a localized area. When the screw isinserted, it deforms the material of the rib, or cuts a thread allowingit to lock into the implant.

FIG. 3C illustrates an additional feature according to some embodimentsof the invention. As shown, a bone nail is formed with a longitudinalslot 152, for example, at its proximal end 34. After the nail has beenattached to the broken bone at its distal end, for example by a bonescrew extending through hole 46 (see FIG. 2), and the broken parts ofthe bone have been aligned, the surgeon can apply compression to thefracture site by attaching a screw to the bone through slot 152 andpulling the nail against the screw in the slot, optionally using theimplant insertion tool. One or more other screws at the proximal end maythen be added, for example, through hole 38, to anchor the nail.

According to some embodiments of the invention, slot 152 may include aridge or rib 154 to prevent withdrawal of the screw from the slot, as inthe case of the round screw hole described above.

Referring now to FIGS. 4 and 5, there are shown alternativeconstructions for a connector for an implant insertion tool or handle.In one illustrative embodiment, a connector 70 shown in FIG. 4 includesa grouping of radial slots 72 (for example, three as illustrated), whichare configured to engage a complementary end of a conventional implantinsertion tool (not shown) in the required orientation, according toconventional implant insertion practice. Preferably, more than one slot72 is employed; as composite materials generally provide limited shearstrength relative to metal, and multiple slots help assure sharing ofthe shear load imposed by the torque applied by the insertion handle.Alternatively, more than three slots 72 may be employed, provided theyare arranged at the proper orientation relative to the insertion handle.

In another illustrative embodiment shown in FIG. 5, connector 76 mayhave a single position at which it can connect to the insertion tool.Illustratively, this may be a generally hexagonal external configurationindicated at 78 capable of bearing torsion.

In the exemplary embodiments illustrated, connectors 70 and 76 areformed of the same reinforced polymer material as the rest of theimplant body. Optionally, the connectors may be formed of a metal endattachment (for example, titanium or the like) or ceramics molded intothe proximal end of the implant body, provided it does not interfereunacceptably with CT or MRI visualization

According to some embodiments of the invention, bone implants asdescribed in connection with FIGS. 1-5, are formed of fiber layersdesigned to resist mainly bending forces, and mainly torsional forces.(As previously mentioned, the term “mainly” is considered to mean thatthe forces encountered are at least about 75 percent bending forces orat least about 75 percent torsional forces.)

FIGS. 6A, 6B, and 6C show some details of a bone nail 89 according tosuch embodiments.

Here, core 90 and an outer layer 92 are formed of long substantiallylinearly extending fibers parallel to a longitudinal axis 94 within apolymer matrix.

In the embodiments of FIGS. 6A, 6B and 6C, the nail is cannulated forillustrative purposes. Optionally, an internal lumen 114 is covered witha metal layer 130, for example, a metal tube, optionally inserted duringcompression molding of the nail.

Alternatively, in some embodiments, the nail is non-cannulated. In suchembodiments, the core may be solid, but may be otherwise the same ascore 90 illustrated.

Referring to FIG. 6B, core 90, are multiple layers 100 of filaments in apolymer matrix helically wound in opposite directions, example, at ±45degrees. Layers 100 are optionally wound or braided after manufacturingthe longitudinal core 90. Optionally this may be formed by windingimpregnated strips of composite material. One or more layers oriented inopposite direction are employed to resist the torque applied on the nailin the two directions of rotation. Optionally, at the proximal end 104,layer 100 is comprised of helically oriented filaments formed by windingmultiple layers of impregnated strips of composite material in oppositedirections, for example, at approximately +45 and −45 degrees.

It should be noted that some variability in the direction of the fibersis optional. For example, the windings 100 may be oriented at angles inthe range of ±35 to 55 degrees.

Optionally, fibers may braided to combine two neighbor layers.

Optionally, the outer surface may be coated, at least partly, forexample by plating, with a layer 110 of titanium, tantalum or similarmetal

Optionally metal outer surface 110 may be manufactured by compressionmolding the composite into a metal shell.

Referring to FIG. 6C, the distal end 106 may be of the same constructionas the proximal end. Illustratively, however, it is shown without ametal layer, and with only two helical layers 112.

As an example of the construction illustrated in FIG. 6A, for anintramedullary nail having an outside diameter of 8.5 mm, the inner,linear fiber layer embedded within the polymer matrix may have adiameter of up to 7.6 mm. If the nail is cannulated, internal lumendiameter may be 2.7 mm, metal cover (if any) will be between diameters2.7 to 2.9 mm. The second layer of helical fibers may have a thicknessof 0.3 mm between diameter 7.6 mm and diameter 8.2 mm. The third (outer)layer of linearly extending fibers embedded in a polymer matrix may havea thickness of 0.15 mm between inner and outer diameters 8.2 mm and 8.5mm.

As an example for cannulated nail having a proximal head with a finaldiameter of 11.6 mm, an inner lumen may have a 2.7 mm diameter, metalcover (if included) will be from 2.7 to 2.9 mm in diameter, linear fiberlayer may have a diameters from 2.9 up to 7 mm. A first helical in −45deg, orientation may be from 7 to 7.4 mm in diameter. A second layer ofhelical fibers in +45 deg, may be from 7.4 mm to 7.8 mm in diameter. Onemore helical layer in −45 deg. may be from 7.8 to 8.2 mm in diameter,one more helical layer in +45 deg may be from 8.2 to 8.6 mm in diameter,and helical circular layer may be between 8.6 and 10.8 mm in diameter.An outer layer of longitudinal fibers may be between 10.8 mm and 11.6mm. in diameter.

Optionally, according to some exemplary embodiments, and as shown inFIGS. 6A-9B, a nail 107 may be cannulated. One optional use for acannulated nail is repair of long bones such as the femur, tibia andhumerus. As illustrated, in FIGS. 7-9B, nail 107 includes an elongatedbody 109 having a proximal end 110, a distal end 113, and asubstantially central, axially extending lumen 114

Distal end 113 includes a longitudinal slot 116 and a round hole 118extending in the same direction through the nail, and round holes 120 aand 120 b extending at a 90 degree angle to slot 116 and hole 118.Proximal end 110 includes round screw holes 122 and 124, and a slot 126.

Each of the screw holes and slots at distal end 113 and proximal end 110of nail 107 may include radiopaque location markings. As seen in FIG.9B, these may take the form of rods or pins 128 as described inconnection with FIGS. 2A and 3C, or rings as described in connectionwith FIGS. 3A and 3B. Additionally, or alternatively, a thin metal tube130 may be bonded in any suitable manner on the inner surface of lumen114 (the distal end of which is best seen in FIG. 9B).

As in the case of the embodiments employing wire 59 shown in FIG. 2, oremploying the radiopaque filler in the matrix, the continuity of tube130 is interrupted by the screw holes and the slots, so that thelongitudinal positions of these passages is indicated under fluoroscopyby the resulting discontinuities. As will be appreciated, tube 130 alsoserves to mark the location and extent of implant 107 itself.

Cannulated implant 107 is otherwise the same as that previouslydescribed in connection with FIGS. 1, 2, and may include a connector atits proximal end 110 like that described in connection with FIGS. 4 and5, and an end cap as described in connection with FIG. 2B. Also, it maybe formed with the same layer configuration as in FIG. 6A. Accordingly,further description is omitted in the interest of brevity.

Optionally, implants according to some embodiments of the invention mayinclude additional elements to improve performance, mainly strength. Forexample, an insert can be made of metal or ceramics, or isotropiccomposite parts. One such embodiment is illustrated by way of example,in FIGS. 10A-10C.

In FIG. 10A, there is shown an intramedullary nail 132 including a metalnut 134 to impart added strength to the connection between the implant,and the insertion handle. This may be embedded optionally into theimplant during molding. Optionally, the nut 134 may by inserted into theproximal slot, and pushed into the proximal side of the nail.

In FIGS. 10B and 10C there are illustrated one option of the nut insert134. As shown, nut 134 is generally T-shaped with a body 135 and opposedarms 136. When not molded in, nut 134 is oriented as shown in FIGS. 10Band 10C, and placed in slot 137 near its distal end 138. It is thenmoved in the proximal direction so that body is within the axial bore atthe proximal end 139 of the implant.

Alternatively, or additionally, the surface of the implant may beprovided with a metal coating or plating 141. The metal insert and thecoating may be formed of titanium, titanium alloy or tantalum, or anyother suitable and desired metal or metal alloy.

FIG. 11 illustrates the construction of a bone plate 160 according tosome embodiments of the invention. Plate 160 is comprised of alongitudinal fibers coated with one, two, three, four layers of ±45°longitudinal wires, longitudinal fibers coated by one, two, three, fourlayers of woven or braided ±45° layers. As an example, plate 160 iscomprised of a woven or braided body 162 formed of substantiallylinearly extending comingled long carbon and polymer filaments in athermoplastic polymer matrix as previously described. Passages 170 areprovided to receive bone fixation screws (not shown). Optionally,passages 170 are formed in the molding process when plate 160 isfabricated. Alternatively, passages 170 are formed by machining afterthe plate has been fabricated.

Passages 170 may be threaded or non-threaded or a combination of thetwo. Optionally only a portion of some or all the passages are threadedwith the other part is non-threaded, and designed to engage with thescrew head.

According to some embodiments of the present invention, bone plate 160is preformed based on average anatomical data, and then bent to a finalshape before implantation based on specific anatomical data concerningthe actual implant site for a particular patient. According to someexemplary embodiments, the final shaping is done by heating thepre-formed implant in a molding press with suitably shaped inserts.Force is applied to bend the plate to the required shape, and then themold is cooled in a manner which allows the implant to retain its bentshape without substantial change in its other properties. As an example,a bone plate formed of carbon fibers, in a PEEK matrix, is heated to380-400 Deg C., held at temperature for 5-30 minutes as needed to effectproper bending, then cooled at a rate of 5-30 Deg C. per minute to 150Deg C., and then cooled rapidly to room temperature.

Optionally, specific anatomical data for shaping plate 160 is obtainedby direct measurement of the patient's implant site during a surgicalprocedure, or even visually.

Alternatively, the specific anatomical data is obtained radiologicallyor by an MRI or by CT of the patient's implant site.

FIG. 12A-12D illustrate a bone fixation screw suitable for use with thevarious implant embodiments described above, or as standalone forfixation of fractures without an implant. The illustrated screws may beformed of the same fiber reinforced or self reinforcing polymermaterials as described above.

As illustrated in FIG. 12A, the screws are comprised of a core 145having long fibers extending in longitudinal direction, parallel to thescrew axis 143 embedded in a polymer matrix. The thread 144 is made fromcomposite material having long fibers, wound with the threads.Optionally some fibers may cross from the core and interweave into thethread as shown at 147, to increase the strength of the thread base 149.

Optionally, the thread 144 can be made of composite material withchopped fibers, optionally molded over the screw core.

The screw connector 148 for engagement with the closing and openingtool, may be of any conventional shape, for example, an internally orexternally threaded hexagon, Phillips head, slotted, axial crown, andthe like. Optionally the head of the screw may be a metal insert.

FIG. 12B illustrates a bone fixation screw 142 a, having a helicalcomposite material layer 150, preferably with long fibers directed in+/−45 deg relative to the axis 143. That layer may be included to addresistance to the torque applied on the screw during insertion orremoval. Optionally layer 150 will comprise a winding only with onehelical direction. Optionally the two fiber directions +/−45 deg arebraided.

FIG. 12C illustrates a screw 142 b providing added shear strength, byhaving metal shell 152 outside composite core 145. Shell 152 may besolid, and comprise the entire thread with no composite component. Sucha structure provides the strength of the metal to resist shearing of thethread, and the strength of the composite core to resist bending.Optionally the distal end of the screw will be part of the shell 154,and optionally, may be self tapping.

FIG. 12D illustrates a screw 142 c having the threads 144 coated with athin layer 156 of titanium, or other metal such as titanium alloyTi6A14V , or any other biocompatible metal or metal alloy. The metalcoating should be thick enough to provide the needed additionalstrength, but thin enough that it does not cause artifacts in CT imagesor MRIs. Coating thicknesses in the range of about 0.02 to 0.2 mmprovide satisfactory results. As a specific example, the coating mayhave a thickness of a 0.1 mm.

The coating layer 156 may be formed in various ways including byelectrochemical coating, physical vapor deposition, plasma spraying,molding the composite material into a metal shell etc. Whatevertechnique is employed, the coating should be made a smooth as possible,as a smooth surface is found to prevent attachment of re-grown tissue orbone to the threads, which would hinder removal of the screw if theimplant must later be removed.

Optionally, bone screw can be made in any combination of the structuralcomponents described above.

Optionally, bone screw, in any combination can be canullated, with aninternal lumen sized for use with guide wire.

FIG. 13A illustrates the construction of a proximal femur (PF) nail 180formed of a reinforced polymer matrix, optionally including an embeddedreinforcing insert as described above in connection with otherembodiments of the invention. PF nails are used for repairing fracturesinvolving the femur.

As illustrated, PF nail 180 includes an elongated stem 182 having aproximal end 184 with at least one passage 186 oriented at an angle to alongitudinal axis 284 of the nail. In use, passage 186 receives aproximal end bone fixation screw 286 which anchors the nail in the neck188 and head 189 of the femur.

Optionally, PF nail 180 includes a threaded passage 190 to receive ananti-rotation pin 288. Passage 190 extends parallel to proximal endfixation screw passage 186.

Optionally, according to some exemplary embodiments of the invention,passage 186 is also threaded and receives a holder 192 within which legscrew 187 is slidingly received.

It should be understood that in addition to passages 186 and 190, a PFnail typically includes additional passages, such as passage 290 at adistal end 292. In use, passage 290 receives a bone fixation screw foranchoring PF nail 180 to a lower portion of the femur. Optionally otherpassages (not shown) may extend at an angle, for example, 90 degrees, topassage 290.

As in previously described embodiments, PF nail 180 may includeradiopaque markings for some or all of the passages.

Optionally according to some exemplary embodiments of the invention, PFnail 180 includes an insertion tool connector 294 as described above,and an end cap 296 configured to be received in connector 294 after PFnail 180 has been implanted to prevent bone internal bone or tissueregrowth.

Exemplary embodiments of leg screws are shown in FIGS. 13B and 13C.Optionally, leg screws according to some embodiments of the invention,are formed of a core of the same composite material and the nail.Optionally, the screw is formed of metal, for example, a titanium alloysuch as Ti-6A1-4V.

As shown in FIG. 13B, a leg screw 300 includes a reinforced polymer core302, and a surrounding metal shell 304. Optionally, core 302 may includean internal lumen 306 intended to receive a guide wire (not shown) forassisting the surgeon during the implant procedure.

Shell 304 includes threads 308 at least at its distal end 309 forinterlocking with the surrounding bone. Optionally, the threads are selftapping. Threads 308 may be formed only in shell 304 or may beinternally relieved so that the polymer core 302 penetrates the threads,as best seen at 310 in FIG. 13C. In some instances, this may reduce theamount of metal in the shell for improved CT imaging and MRIvisualization, and may help increase the strength of the connectionbetween the screw core and the shell. The interface between the core andthe shell may also include recesses and complementary projections ofvarious shapes (not shown) to provide for stress sharing.

Optionally, as also illustrated in FIG. 13C, at 312 and 314, the metalshell 316 is crimped around proximal and distal ends 318 and 320 ofpolymer core 322.

FIGS. 14A-14C show an implant removal tool 200 according to an aspect ofsome embodiments of the present invention. Removal tool 200 isconfigured to engage an installed implant 202 through the axialconnector opening 204 at the proximal end 206 of the implant. For thispurpose, axial opening 204 communicates with a transverse slot 208 aspreviously described.

As seen in FIG. 14B, tool 200 includes first and second arms 210 and212, having respective transverse tips 214 and 216 at their distal end,and a suitable handle (not shown) for easy manipulation at theirproximal ends. Arms 210 and 212 are connected by a pivot intermediatethe proximal and distal ends and thus provide a scissor mechanismoperable to move tips 214 and 216 between retracted and extendedpositions. In the retracted position, the tips are close to each otherso that the distal end of tool 200 is easily insertable into opening204. In the extended position, tips are separated, and engage theopposite sides of slot 208.

As will be understood, in the extended position axial, force can beapplied to withdraw implant 202 from inside an opening in a bone.

FIGS. 15A and 15B show a bone drilling assembly 230 used to prepare animplant site to receive a bone implant according to some embodiments ofthe invention. The illustrated construction is designed to minimizeinterference with fluoroscopic visualization of the drilling site by thesurgeon.

Drilling assembly 230 includes a power unit 232 which drives a drill bit234. An angled connector 236 is configured to be fitted between powerunit 232 and drill bit 234. As best seen in FIG. 15B, connector 236includes a female coupling 238 for connection to drill bit 234, and amale connector 240 for connection to power unit 232. These are mountedin a body 246 formed a polycarbonate or other suitable radiolucentmaterial. A flexible cable 242 formed of for example multi-filaments ofstainless steel or other suitable material is also mounted in body 246and transfers torque from coupler 240 to coupler 238.

Still referring to FIG. 15B, connector 236 is angled at 250 so thatcouplers 238 and 240 are oriented, for example, at 90 degrees to eachother. This allows power unit 232 to remain outside the fluoroscopyimaging range, and therefore does not interfere with visualization bythe surgeon of the drilling site.

Couplers 238 and 240 are of conventional design, or of any othersuitable and desired type. According to some embodiments, couplers 238and 240 include outer sleeves 252 and 254 formed of Teflon or the like,which serve as bearings to minimize friction during rotation. Cable 242is sized to rotate freely relative to the body 246 Optionally, insteadof a flexible power transfer connection, rigid elongated rods connectedtogether by suitable right-angle gear arrangement, may be employed.Preferably these parts are also formed of radiolucent material.

According to some embodiments, drill bit 234 may be made of a reinforcedpolymer matrix, optionally, including longitudinally extendingreinforcing fibers as described above, coated with hard metal such astitanium, or diamond.

Power unit 230 may be a standard operating room drill. Optionally angledconnector 234 may include a self-contained, electric motor, gear andbattery, in that device, a separate power unit 232 is not needed.

Optionally, the connector 236 constructed is provided in sterilepackaging, and is intended for disposal after a single use.

Optionally, as illustrated in FIGS. 16A-16G, the nail at the proximalend is connected to the insertion handle with a bayonet connection.Optionally, the proximal end nail includes longitudinal grooves 162 inorder to insert the bayonet teeth 165 on the tube or rod 164 whichconnects the nail to the handle. Tube 164 rotates inside the nail in itsradial groove 163. A nut 166 fastens over the tube 164 to tighten thenail to the handle. Optionally, the nail proximal end does not includelongitudinal grooves for insertion of the bayonet teeth. Instead, tube134 includes expandable bayonet teeth.

FIG. 17A and FIG. 17B illustrate a way to reduce cost during productionof composite intramedullar nails. The nails are supplied in many lengthsand diameters for humerus, tibia and femur bones, and are usually curvedto follow the anatomic shape of the bones. However, it is less costly tomanufacture straight nail, with all or most of the layers, and add afinal manufacturing step of bending the nail.

FIG. 17A illustrates a bending tool 170. As shown, tool 170, includes acavity 171 to receive a straight nail. The tool has electric heaters 172heating the tool with the nail inside to a suitable plastic deformationtemperature. For example for a nail formed of PEEK, a suitabletemperature is in the range of 380 to 410 deg C. Optionally pressure maybe applied to the nail during heating, for example by pressing the nailaxially via opening 173. The tool has two halves 174 and 175 defining amold cavity, made of material capable to bend without damage, at theprocess temperature, such as Nitinol.

At high temperature, the tool bends the nail. FIG. 17B illustrates thetool after bending. The nail is cooled within the tool, and theresulting curve 176 is retained.

PEEK and similar materials can be amorphous or crystalline to somedegree, as determined by the desired heating and cooling treatment.Bending tool 170 has controller not shown, to establish the desiredheating and cooling protocol.

After cooling, the tool opened along surface 177, and the curved nail is

FIG. 18 shows an example of a drill guide and insertion tool 398 for usewith an implant 400 according to some of the implant embodiments asdescribed above. As shown, tool 398 is comprised of a body 402 having adrill guide holes 404 and a coupling portion 406 which engages thecoupler portion 410 of implant 400. Included in coupling portion 406 isan alignment element adapted to engage with a complementary element ofthe connector 410 to permit interconnection of the tool and the implantin the single orientation referred to in connection with FIGS. 4 and 5.

As various features of devices and methods have been described. It willbe appreciated by persons skilled in the art that the present inventionis not limited to what has been particularly shown and describedhereinabove. Rather, the scope of the present invention includes bothcombinations and subcombinations of the various features describedhereinabove, as well as variations and modifications thereof that arenot in the prior art, which would occur to persons skilled in the artupon reading the foregoing description.

It should also be appreciated that some of the embodiments are describedonly as methods or only as apparatus, however the scope of the inventionincludes both methods for using apparatus and apparatus for applyingmethods. The scope of the invention also covers machines for creatingthe apparatus described herein. In addition, the scope of the inventionalso includes methods of using, constructing, calibrating and/ormaintaining the apparatus described herein. When used in the followingclaims or in the text above, the terms “comprises”, “comprising”,“includes”, “including” or the like mean “including but not limited.”

The invention claimed is:
 1. A bone fixation screw comprising: acomposite core formed of a threaded, polymer body containinglongitudinally extending reinforcing fibers; and a metal exteriorsurface on the core to provide additional hardness to the screw; whereinsaid metal exterior surface is thin enough so that it does not causeartifacts in CT or MRI images that would significantly interfere withvisualization, having a thickness ranging between 0.02 and 0.1 mm; andwherein said metal exterior surface is smooth.
 2. A bone fixation screwaccording to claim 1, wherein the metal surface is titanium or atitanium alloy.
 3. A bone fixation screw according to claim 1, whereinthe metal surface is threaded with screw threads.
 4. A bone fixationscrew according to claim 3, wherein a portion of the composite corepenetrates an inner surface of the metal threads.
 5. A bone fixationscrew according, to claim 3, wherein an interface between the compositecore and the metal surface includes complementary projections andrecesses.
 6. A bone fixation screw according to claim 3, wherein thescrew threads are oversized or mismatched in pitch relative to screwholes in a bone implant configured to receive the screws.
 7. A bonefixation screw according to claim 1, wherein the material comprising themetal surface is crimped around proximal and/or distal ends of thecomposite core of the screw.
 8. A bone fixation screw according to claim1, wherein the metal surface adds strength to said screw.
 9. A bonefixation screw according to claim 1, wherein said bone screw has aself-tapping tip.
 10. A. bone fixation screw according to claim 9,wherein said self tapping tip is covered by said layer.
 11. A bonefixation screw according to claim 1, wherein said screw is cannulated.12. A bone fixation screw according to claim 1, comprising an implantwhich adds hardness to the screw.
 13. A bone fixation screw according toclaim 12, wherein said implant is embedded in the screw.
 14. A bonefixation screw according to claim 1, wherein said body includes amaterial layer between said body and said metal layer.
 15. A bonefixation screw according to claim 14, wherein said layer comprises acomposite material with helically wound fibers at an angle of +−45degrees.
 16. A bone fixation screw according to claim 1, wherein saidmetal layer is crimped on said screw.